I think that you might have a little more success with finding testers and getting feedback if you actually told people what was changed and not takeing the look for yourself apporve like above.  I know that you specifically mentioned the authorize.net but if you have a changepoint list then people would know what they need to be testing and could possibly speed up the testing process and keep you from looking bad by using the "It's comming in two weeks" approch.

You are both right and we will publish a changelog, but the XHTML compliancy has induced changes in all and every piece of code. So I cannot tell you that we need testing new features more than any other part of the module - except payment providers, that we know need more feedback.